rocs: init at 18.12.0

[KnairdA]

Motivation for this change

Derivation for Rocs was missing despite the source being referenced in pkgs/applications/kde/srcs.nix.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.

---

[Ma27]

The startup of rocs breaks in my rather minimalistic environment (without KDE) with the following error:

qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in ""
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

[1]    10176 abort      ./result/bin/rocs

A common workaround for this is to wrap QT_PLUGIN_PATH in a postInstall hook using wrapProgram. The full issue is described in #44047.

[KnairdA]

Thank you for the explanation. I added the required plugin paths using wrapProgram and it now works even when PATH and QT_PLUGIN_PATH are undefined in the environment. I first tried testing this in a pure nix-shell but the GUI could not be initialized (setting DISPLAY was not enough to fix this).

Any suggestions on how to quickly obtain a more minimal environment? Weirdly my desktop environment doesn't explicitly use any part of KDE but the relevant paths seem to have leaked in via some other way.

[Ma27]

Any suggestions on how to quickly obtain a more minimal environment? Weirdly my desktop environment doesn't explicitly use any part of KDE but the relevant paths seem to have leaked in via some other way.

Admittedly I don't know. This seems to be somewhat KDE related, I tested avidemux (QT5 based), firefox and dolphin (at KDE application). The only breaking application was dolphin. But I assume that this can be fixed in #44047.

I'll test rocs to see if it works in my environment, but then I'd merge :)

[Ma27]

ok so to test I tried the following file: https://github.com/KDE/rocs/blob/master/Examples/BreadthFirstSearch/bfs.rocs (downloaded with View Raw).

I get the following messages on the console when I try to open it (and nothing else happens in the UI):

org.kde.kcoreaddons: KDirWatch: "/tmp/rocs-dxyQLx" is a directory. Use addDir!
Graph document index invalid, aborting change of current document.
org.kde.rocs.graphtheory.general: "qrc:/libgraphtheory/qml/Scene.qml:22 module \"QtQuick.Controls\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:24 module \"QtQuick.Dialogs\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:21 module \"QtQuick\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:23 module \"QtQuick.Layouts\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:25 module \"QtQml.StateMachine\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:22 module \"QtQuick.Controls\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:24 module \"QtQuick.Dialogs\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:21 module \"QtQuick\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:23 module \"QtQuick.Layouts\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:25 module \"QtQml.StateMachine\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:22 module \"QtQuick.Controls\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:24 module \"QtQuick.Dialogs\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:21 module \"QtQuick\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:23 module \"QtQuick.Layouts\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:25 module \"QtQml.StateMachine\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:22 module \"QtQuick.Controls\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:24 module \"QtQuick.Dialogs\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:21 module \"QtQuick\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:23 module \"QtQuick.Layouts\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:25 module \"QtQml.StateMachine\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:22 module \"QtQuick.Controls\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:24 module \"QtQuick.Dialogs\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:21 module \"QtQuick\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:23 module \"QtQuick.Layouts\" is not installed\nqrc:/libgraphtheory/qml/Scene.qml:25 module \"QtQml.StateMachine\" is not installed\n"

[aanderse]

@KnairdA are you motivated to continue with this PR?